The Bank Manager ver 3

[Tally Ho]

Is there any difference between a regular LiFePo battery and the minis? Is one preferred over the other?

Generally, no big difference other than how tight the cells are in the case and how much “filler “ is used in the case. It is strange to watch guys cut open different form factor LFP batteries, just to find empty space in the case, usually with some sort of foam filler.

I think batteries using prismatic cells all need the same space for the actual cells, but then group 31 batteries (all 100 Ah) gets more filler in the case than a group 27 form factor. And a mini has the same 4 cells, with essentially no spacers, filler, etc.

I like the minis only because of the smaller form factor. I am looking at a 314 Ah battery to replace my old golf cart batteries (215 Ah capacity) in about the same footprint and since LFP, also much lighter than lead acid.

Greg

 

[Hayden Watson]

Thanks Dave. That was my understanding that the Hitachi alternator produces approximately 50% of its rated output once it reaches operational temperature. I can foresee a Balmar 100-amp alternator with external regulation in the future.

I basically see that there are two good and workable philosophies to have an LFP house and FLA start setup.

1. If you have an internally regulated alternator, you charge to the FLA start and use a DC-DC charger to charge the LFP house. As has been said, this limits the current from the alternator sufficiently to prevent it from cooking itself and provides the needed uninterruptable buffer for the diodes. The downside of this is that you will get very little charge from your engine runtime and it will require many hours to return the needed charge.

2. If you have a high output alternator, you can protect it with a sophisticated regulator such as the Zeus or Wakespeed to prevent overheating and to set the charge parameters so that it is not likely to hit the OVP voltage. This is the way that I have gone. I isolate the 560Ah LFP start battery from the 100Ah Group 31 AGM with an ArgoFET battery isolator. The charge profile for the AGM is also perfect for the LFP and because the AGM will always be connected to the alternator there is no worry about diode boom with an OVP.

My system is a 250A large frame alternator driven by my 23-hp diesel with a Zeus. I can recharge from 5%SOC to 100% in just over 3-hours. This did require installing a serpentine belt and modifying the belt tensioner.

 

[dlochner]

I basically see that there are two good and workable philosophies to have an LFP house and FLA start setup.

1. If you have an internally regulated alternator, you charge to the FLA start and use a DC-DC charger to charge the LFP house. As has been said, this limits the current from the alternator sufficiently to prevent it from cooking itself and provides the needed uninterruptable buffer for the diodes. The downside of this is that you will get very little charge from your engine runtime and it will require many hours to return the needed charge.

2. If you have a high output alternator, you can protect it with a sophisticated regulator such as the Zeus or Wakespeed to prevent overheating and to set the charge parameters so that it is not likely to hit the OVP voltage. This is the way that I have gone. I isolate the 560Ah LFP start battery from the 100Ah Group 31 AGM with an ArgoFET battery isolator. The charge profile for the AGM is also perfect for the LFP and because the AGM will always be connected to the alternator there is no worry about diode boom with an OVP.

My system is a 250A large frame alternator driven by my 23-hp diesel with a Zeus. I can recharge from 5%SOC to 100% in just over 3-hours. This did require installing a serpentine belt and modifying the belt tensioner.
View attachment 235344

There is one other viable option to prevent alternator damage, use an Alternator Protection Device. In the unlikely event of a BMS shutdown the APD will prevent the diodes from being damaged. Balmar and Sterling make them.

 

[kloudie1]

Yup and the minis aren't all the same dimensions..

 

[Hayden Watson]

There is one other viable option to prevent alternator damage, use an Alternator Protection Device. In the unlikely event of a BMS shutdown the APD will prevent the diodes from being damaged. Balmar and Sterling make them.

This is true but then you would still need to buy a DC-DC charger to go to the start LFP. I like the battery isolation because it requires fewer components and provide the max charge to both banks.

 

[JBP-PA]

LFP batteries used to all use prismatic cells (they have individual cases that provide mechanical protection). The higher capacity batteries, which is what I think you mean by "mini", pack more cells into the same size case by using 'pouch' or 'foil' cells that do not have individual cases, they will have cells wired in parallel, with 4 groups of cells in series to provide the same voltage as 4 prismatic cells. The main battery case provides mechanical protection, thus allowing more cells. (In both, the cells are bound together in compression device. LFP cells must be kept in compression.) The reliability of pouch cells can vary according to manufacturer and their method of compression. You can see both types in the photos here.

Our Recommended Drop-In LifePo4 Batteries - Marine How To

Rod, What are your Recommended Drop-In Batteries for Marine Use? Disclaimer: I still type with one finger as my left arm is still 100% paralyzed. Typo's happen and I try to edit them when I see them or readers point them out.

marinehowto.com

 

[JBP-PA]

Here is what Battleborn has to say.

Pouch vs. Prismatic vs. Cylindrical? Your Lithium Battery Cell Guide

What's the difference between pouch, prismatic, and cylindrical cells in lithium batteries? Read our guide to find the right battery cell type for your system.

battlebornbatteries.com